The present invention relates to an impact and weather resistant thermoplastic molding material comprising a blend of a polyacrylate rubber graft copolymer and a compatible rigid phase. More particularly, the present invention relates to such an impact and weather resistant thermoplastic molding material, wherein the polyacrylate rubber grafting base comprises a low gel, high swelling index butylacrylate rubber grafted with a rigid phase polymer.
It is previously known to prepare acrylate rubber polymers comprising homopolymers and copolymers of at least one alkyl acrylate having grafted thereto a suitable rigid phase. Preferred acrylate rubber particles comprise homopolymers of butylacrylate grafted with homopolymers of styrene or methylmethacrylate or copolymers of styrene with methylmethacrylate or acrylonitrile or both methylmethacrylate and acrylonitrile. Previously known weatherable resins modified by addition of the aforementioned butylacrylate containing rubbers have provided good physical properties and weather resistance, but generally have resulted in medium to high gloss articles under typical injection molding or extrusion conditions. For many applications, such as the interiors of automobiles and the like, it would be desirable to provide a weather resistant resin having a low gloss or "satin" surface appearance. Accordingly, it is to the attainment of this purpose, that the present invention is directed.
The preparation of impact resistant thermoplastic materials by mixing a hard component (a), comprising a copolymer styrene and acrylonitrile, with a soft component (b), comprising a graft copolymer of a styrene/acrylonitrile mixture onto a polyacrylate, has been disclosed in GB 1,124,911. Such molding materials are generically referred to as ASA polymers.
Numerous modifications and improvements in such ASA polymers have been developed. Suitable processes for the preparation of such improved ASA materials include those disclosed in U.S. Pat. Nos. 4,442,263; 4,456,734; 3,830,878; and 3,661,994. The teachings of the above described United States Patents are herein incorporated in their entirety by reference thereto.